Process of electrolytically manufacturing metallic sulfids



UNITED STATES PATENT @rrrcn.

JOSEPH "IV. RICHARDS AND CHARLES W. ROEPPER, OF BETHLEHEM,

PENNSYLVANIA.

PROCESS OF ELECTROLYTICALLY MANUFACTURING METALLIC SULFIDS.

SPECIFICATION forming part of Letters latent No. 602,873, dated April 26, 1898.

Application filed July 6, 1897. Serial No. 643,542. (specimens) To all whom it may concern:

Be it known that we, JOSEPH IV. RICHARDS, a subject of the Queen of Great Britain, and CHARLES W. RoEPrEn, a citizen of the United States, residents of Bethlehem, in the State of Pennsylvania, have invented a certain new and useful Process for Manufacturing Metallic Sulfids Electrolytically, whereof the following is a specification.

Our invention relates to the manufacture of metallic sulfids, and has for its object to cheapen the production of these compounds as commercial articles and also to obtain them, in the case of those sulfids which are useful as pigments, in the condition in which they are most desired for this purpose. The proccss by which we accomplish this is one of extreme simplicity and directness and also one in which the physical conditions attending the production of the sulfids (such as temperature, velocity of production, and concentration of the solution) are easily controlled,with a corresponding resultant economy of material and superior quality of product.

The general principle of our invention consists in employing the metal whose sulfid it is desired to obtain as an anode in the electrolysis of a solution containing a hyposulfite salt, the sulfid sought for being thus formed from the anode and precipitated. In case a complex sulfid is desired the anode is formed of an alloy of those metals whose mixed sulfids are to be obtained.

In describing the process specifically we will choose as an instance the production of cadmium sulfid, which, as is well known, constitutes, commercially, the pigment known as cadmium-yellow. The anode is made of metallic cadmium and may be cast in such shape, whether flat, square, or round, as may be desired. A carbon electrode maybe used as cathode, or any other suitable substance not attacked by the electrolyte or the products set free upon it. Metallic cadmium itself fills these requirements and may be used as a cathode. As electrolyte we employ a solution of of manufacture.

fite other soluble hyposulfites may be employed with the same results. As the electrolysis proceeds the hyposulfite is decomposed, hydrogen being set free at the cathode, while the nascent sulfur combines with the metal of the anode, forming a sulfid, which, as it is insoluble in the solution, deposits in the vessel.

' The shape and arrangement of the electrolyzing apparatus are immaterial and may be adjusted to suit the convenience of the operator. The precipitated sulfid should from time to time be removed from the bottom of the tank, when it may be successively filtered, washed, dried, and pulverized. The solution which is filtered out may, if it still contains hyposulfite, be poured again into the electrolytic tank.

In the case of some sulfids, and among them is cadmium sulfid, we have found that the precipitate is of the best color when it is formed from a hot electrolyte, say, at 7 5 Centigrade. In the case of other sulfids, as in the case of antimony sulfid, a better color is obtained from a cold solution than from a hot one. The presence of other soluble salts in addition to the hyposulfites frequently promotes the formation of the precipitated sulfid and improves its physical condition. Thus in the case of cadmium sulfids we have found that the addition of five per cent. of sodium chlorid to the electrolyte increases its conductivity, rendering the process more rapid and etficient, while at the same time it produces a precipitate of a brighter shade of yellow.

Our process is applicable to the production of all metallic sulfids except those which are soluble in the solution which is used as the electrolyte.

We .are aware that it is common practice to make metallic sulfids by purely chemical means-such as dissolving the metals in acid, passing hydrogen sulfid through the solution and collecting the precipitated metallic sulfid. We are also aware that it has been proposed to use a metal as an anode in a solution containing an acid constituent capable of forming a soluble salt with the metal, thus bringing the metal into solution and to then simultaneously pass into the solution hydrogen sulfid, the metallic sulfid being precipitated.

lution of the metallic salt is obtained electrolytically instead of chemically. These processes are further objectionable in that they necessitate the employment of hydrogen sulfid. The process invented by us differs from these in that the sulfur necessary to form the insoluble metallic sulfid is'furnished by the direct electrolysis of a hyposulfite solution.

We are also aware that it has been proposed to convert by electrolysis a hyposulfite of a metallic base, such as silver, into a sulfid of the same base. Such a process involves the limitation that it is applicable only to those metallic bases whose hyposulfites are soluble, and also'the further necessity of obtaining this metallic base in solution. Our process differs from this in that the metallic base which is supplied is subjectto no other limitation than that it is capable of acting as an anode and wholly independent of the nature of the hyposulfite solution. Our process further differs from this in that the precipitate is obtained free from finely-divided metal or other impurities. By the electrolysis of a hyposulfite solution containing in itself the metallic element the electrolytic decomposition which ensues deposits a certain quantity of pure metal in the region of the cathode. This precipitate mixing with the precipitated sulfid results in an impure product. Our process results in obtaining a product free from any precipitated metal. It is in this sense that the Word pure is used in our claim.

Having thus described our invention, we claim.

The process of manufacturing pure metallic sulfids which consists in employing an anode of or containing the metal or metals Whose sulfid is desired in a solution containing a hyposulfite salt as anelectrolyte in con- 7 junction with any suitable cathode; passing a current of electricity therethrough; and precipitating the sulfid of the metallic base present in the anode, substantially as described.

JOSEPH W. RICHARDS. CHARLES XV. ROEPPER. Witnesses:

. E. REESE,

JAMES H. BELL, C. H. SCHWARTZ. 

